The present invention relates generally to a driver assistance system for facilitating steering of a vehicle by tracking a target line on the surface of a roadway, and more particularly to a lateral control of a vehicle for lane-following system based on detection of lane markings (usually painted white or yellow lines) on the surface of a roadway.
A number of technologies for lateral control by detection of lane markings have emerged. Some of such technologies are disclosed in U.S. Pat. No. 5,913,375, U.S. Pat. No. 5,765,116 and U.S. Pat. No. 5,979,581. In U.S. Pat. No. 5,913,375, a CCD camera mounted on a vehicle detects the presence of lane markings on a roadway and carries out a lateral control of a vehicle in relation to the detected lane marking. In U.S. Pat. No. 5,765,116, a video camera or a CCD camera is used to detect the presence of lane marking. An associated signal processor estimates the vehicle lateral position in relation to the detected lane markings. An electric motor coupled to the steering mechanism is used to provide a torque input to the steering. A controller is designed to assist the driver to maintain the vehicle lane position using a torque input to the steering. In U.S. Pat. No. 5,979,581, a laser sensor is used to detect three points on a painted lane marking on the surface of a roadway and three points are used to estimate the position of the lane centerline relative to the vehicle, as well as the geometry of the roadway.
JP-A 10-103935 discloses a technology to estimate a curve of a lane in a road constructed with a slope rising to the outside edge by correcting image from an image pick-up mounted on a vehicle. This technology is used to correctly estimate the lane centerline used for vehicle lateral control for lane following.
Most of these technologies rely on the lane centerline for lateral control of a vehicle. Some drivers may feel uneasy or uncomfortable being deviated from their favorite lane positions if they are guided toward the lane centerline. Therefore, a need remains for a new approach to the lateral control of vehicles, which allow drivers favorite lane positions. The present invention satisfies this need.
An object of the present invention is to provide an automated lane-following system, which allows drivers favorite lane positions.
According to one aspect of the present invention, there is provided a lane-following system of facilitating steering of a is vehicle by tracking a lane of a roadway, the vehicle having a steering system including a steering mechanism, said lane-following system comprising:
a sensor detecting the position of lane marking on the surface of a roadway in relation to the vehicle, said lane marking defining a lane of a roadway;
a signal processor operatively coupled to said sensor to estimate a lateral displacement of a point at a preview distance in front of the vehicle from the detected lane marking;
an actuator coupled to the steering mechanism to provide a steering bias to the steering system, which may either assist or oppose the steer torque from a vehicle driver, in response to a steering control signal;
a steering controller producing said steering control signal based on said estimated lateral displacement to assist the driver of the vehicle to maintain the vehicle at a target line within the lane using steering bias,
said steering controller being operable, when the vehicle travels without lateral control for lane following, to collect said estimated lateral displacement to produce a lateral displacement data,
said steering controller being operable to update the position of the target line using said lateral displacement data.
According to another aspect of the present invention, there is provided a method of facilitating steering of a vehicle by tracking a lane of a roadway, the vehicle having a steering system including a steering mechanism, said method comprising:
detecting the position of lane marking on the surface of a roadway in relation to the vehicle, said lane marking defining a lane of a roadway;
estimating a lateral displacement of a point at a preview distance in front of the vehicle from the detected lane marking;
producing a steering control signal based on said estimated lateral displacement to assist a driver of the vehicle to maintain the vehicle at a target line within the lane using a steering bias;
collecting, when the vehicle travels without lateral control for lane following, said estimated lateral displacement to produce a lateral displacement data; and
updating the position of the target line using said lateral displacement data.